Educational familiarization only. This is original TechOpsBase learning content created from privately supplied legacy training and MSG-3 source material. It does not reproduce manufacturer pages, proprietary diagrams, task steps, numerical maintenance limits, dispatch criteria or controlled maintenance data. Current approved aircraft data, effectivity and operator procedures govern all aircraft work.
Resource profile
- Aircraft: Airbus A350 family
- ATA chapter: 42 — Integrated Modular Avionics
- Resource: A350 ATA 42 AFDX Network Fundamentals
- Level: Intermediate-to-advanced
- Status: Draft pending technical review
Learning objectives
- Explain full-duplex switching.
- Describe dual network A/B.
- Understand end systems and virtual links.
- Recognize deterministic traffic controls.
- Diagnose path-level faults.
1. Purpose and operational value
AFDX provides deterministic, redundant Ethernet-based communication for avionics applications and common IMA resources.
2. Architecture and system flow
Each subscriber uses an AFDX end system connected to two physically separate network paths.
Configured switches forward traffic according to virtual-link definitions rather than learning arbitrary routes like a general office network.
Bandwidth, integrity checks, sequence and policing controls create predictable avionics communication.
3. Major components and functions
AFDX end system
Creates/receives avionics frames for applications. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes port state, A/B interface and virtual-link health. Command, feedback and physical effect must agree before hardware is condemned.
Network A and B
Provide physically independent redundant paths. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes path-specific loss, switches and cabling. Command, feedback and physical effect must agree before hardware is condemned.
AFDX switch
Forwards configured frames. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes power, configuration, port status and policing. Command, feedback and physical effect must agree before hardware is condemned.
Virtual link
Defines one-way logical communication and bandwidth. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes source, destinations, BAG/traffic status and integrity. Command, feedback and physical effect must agree before hardware is condemned.
AFDX harness
Carries full-duplex Ethernet signals. The component must receive the correct input, perform its intended function and provide a valid output or status. A maintenance diagnosis must separate loss of power, loss of communication, incorrect configuration, blockage or leakage, contamination, mechanical degradation and an upstream or downstream interface failure. Useful evidence includes continuity, shielding, quality and connector condition. Command, feedback and physical effect must agree before hardware is condemned.
4. Normal operating sequence
1. Publish
Source application sends data through end system.
2. Duplicate
Traffic is sent across A and B paths.
3. Switch
Configured switches forward to destination ports.
4. Receive/select
Destination end system validates and delivers data.
5. Monitor
NBF and system applications detect connectivity faults.
5. Control, monitoring and protection
The two networks protect against a single path fault but do not guarantee service if the source, destination or configuration is wrong.
A healthy physical link can still fail to carry a specific virtual link because of configuration or policing.
6. Failure modes and maintenance reasoning
- One network lost: A or B switch/cable/end-system path.
- Both paths lost: Common end system, multiple network faults or configuration.
- One virtual link lost: Source/destination/application or configured route.
- Intermittent errors: Cable/connector quality, switch port or end system.
- Traffic rejected: Policing, sequence/integrity or configuration.
7. Interfaces with other aircraft systems
- CPIOM and CRDC end systems.
- FWS/CMS.
- Software/configuration loading.
- Electrical power.
- Aircraft-system applications.
8. Practical maintenance scenarios
A path failed, B continues
Verify degraded network and dispatch status.
Only one application data stream lost
Do not replace every switch; trace the VL.
Physical link good, data absent
Check end-system/application/configuration.
9. Technician takeaways
- AFDX is deterministic and configured.
- Network A/B are independent paths.
- Virtual-link evidence is more precise than general connectivity.
- Physical and logical tests are both required.
Maintenance boundary
This resource explains architecture, operation, indications and system-level troubleshooting. It intentionally excludes removal/installation instructions, wiring-pin checks, maintenance limits, software part numbers, servicing quantities, inspection intervals and release-to-service criteria.
Review prompts
- What is the required system function?
- Which component commands, processes or physically performs it?
- Which power, fluid, pneumatic or data path is required?
- What command proves the function was requested?
- What feedback or physical effect proves correct operation?
- Which adjacent ATA system can create the same symptom?
- What evidence should be preserved before reset, draining, servicing or software action?
- What hygiene, electrical, pressure, network or safety boundary applies?
